Electrical relay



Jan. 17, 1939. MlSHELEVlCH 2,144,543

ELECTR I CAL RELAY Filed July 50, 1937 INVENTOR Benju ishelev'lch 1 @11 HIS I ATTORNEY Patented Jan. 17, 1939 UNITED STATES PATENT OFFICE ELECTRICAL RELAY Application July 30, 1937, Serial No. 156,549

7 Claims.

My invention relates to electrical relays, and particularly to relays which are adapted for flashing danger signals at highway-railroad crossings upon the approach of a train.

More particularly, my present invention relates to relays of the type described having an oscillatable armature which is biased to one of two extreme positions, and one object of my invention is to provide a relay of this type having an equal time period between the operation of the armature from each extreme position to the opposite extreme position to produce a steady and uniform operation of the signals controlled by the relay.

Another object of my invention is to provide in a relay of the type described a simple and enicient means for equalizing any difierences which exist in the time period which elapses between successive armature movements due to the means for biasing the armature to its one position.

Other objects of my invention will become apparent as the description proceeds.

I shall describe one form of relay embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawing, Fig. l is a view, partly in elevation and partly diagrammatic, illustrating one form of relay embodying my invention. Fig. 2 is a top plan view of the relay shown in Fig. 1.

Similar reference characters refer to similar parts in both views.

Referring to the drawing, the relay here shown, which relay is designated as a whole by the reference character A, comprises three magnetizable cores 5, 2, and 3, connected together at their upper ends by a backstrap l, and provided at their lower ends with enlarged elongated pole pieces i 2 and 3 respectively. The core I carries an energizing winding 5, and the core 3 carries a similar energizing winding 6', while the core 2 carries a plurality of closed conductors, here shown as washers l, the number of which serves to determine the time characteristics of the relay, as will be made clear hereinafter.

A magnetizable armature 8 is pivotally supported intermediate its ends directly below the pole piece 2 for oscillation about bearings 9, and is arranged to swing toward one or the other of the pole pieces I and 3 suitable nonmagnetizable stops 8 being attached to the arto prevent the armature from coming into actual contact with the pole pieces. The

armature 8 is constantly biased to the position in which the stop 8 engages the pole piece 3 by means of a counterweight ID, the function of which counterweight will be made clear hereinafter.

Operatively connected to, and moving in uni- 5 son with, armature 8 are two contact fingers H and i2. When armature 8 is swung toward pole piece 3 as shown in the drawing, contact finger I! engages a fixed contact member H to close a contact li-ll, and contact finger I2 10 engages a fixed contact member l2 to close a contact l2l2 When armature 8 is swung toward pole piece l however, contact finger ll then engages a fixed contact member ll to close a contact ll-ll while contact finger l2 engages a fixed contact member 12 to close a contact l2|2 The windings 5 and 6 of relay A are connected in series in such manner that the fiux created 20 by these windings when these windings are supplied with current will thread the core 2 in opposite directions, and the windings are arranged to be at times supplied with current from a suitable source of current, here shown as a battery 25 i, over a suitable control contact which may, for example, be the contact of a control relay, but which is here shown for convenience as a manually operable switch M. It will be noted, however, from an inspection of the drawing, that, when contact |l--Il is closed, winding 6 is short circuited, and that, when contact ll-ll is closed, winding 5 is short circuited.

The operation of the portion of the relay thus far described is as follows: As shown in Fig. 1, switch it is open, and armature 8 is swung toward pole piece 3 due to the bias of the counterweight 50, so that contacts lil l and I2---l2 are closed. If now, switch I4 is closed, current will flow through winding 5, but since contact 40 Hil is closed, winding 6 is short circuited, and winding 6 will therefore remain deenergied. The energization of winding 5 sets up a flux in core l which causes armature 8 to swing toward pole piece i This motion of the armature opens 5 contacts ll-l i and 12-] 2 and closes contacts il-i and l2--l2 The closing of contact Hl l short circuits winding 5, and the field set up in core I by this winding commences to decay. Due, however, to the snubbing effect of the short circuited winding, and to washers I on core 2, this decay is comparatively slow. The opening of contact lll I in the meantime has allowed winding '0 to become energized. The growth of the field set up in core 3 by this latter 5 winding is comparatively slow due to the washers I, but after an interval of time the torque exerted on armature 8 by this flux overbalances the torque exerted on armature 8 by the decaying flux in core 8, so that armature 8 swings toward pole piece 3. This motion first opens contacts H--l l and 12-42 and then closes contacts H-! 6 and I2!2= The field of winding 5 will then slowly build up and the field of winding 6 will sowly decay, this decay being retarded by the self-inductance of winding 6 and the washers i. Eventually the torque exerted by the fiuxin core 3 will not be sufficient to hold the armature and the armature will then again swing toward pole piece l It will therefore be apparent that armature 8 will be swung to and fro as'long :as switch M remains closed, and it will also be apparent that a time interval will elapse between successive armature movements. It will further be apparent that since the flux set up by both windings 5 and ii traverses the common core v2, and since the rate at which the flux builds up and decays in this core depends upon the number of washers l on this core, the time interval which elapses betweensuccessive armature movements may be readily varied by varying the number of washers 1 on core 2.

A relay of the type described is particularly suitable for, although in no way limited to, use for controlling the supply of current to the two lights of the usual flashing light signals which are commonly employed at highway-railway crossings to warn the users of the highway that a train is approaching, andl have accordingly shown the contacts I 2i2 and l2.!'2 arranged for controlling the two flashing lights I5 and It of such a signal. The circuits for these lights will be obvious from an inspection of the drawing, and it willalso be obvious that, whenswitch ldis closed so that the relay is operating, these lights will be alternately lighted or flashed.

When a relay of the type described is -used for flashing the lights of .a highway crossing signal in the manner just described it is desirable that the armature should always occupy one extreme position when the relay is deenergized, so that, if the relay fails to function for any reason when it should be functioning, due for example, to its control circuit being improperly opened, at least one of the warning lights of the signal will be lighted to give a warning indication; and it is for this purpose that the counterweight ID has been provided. I have found, however, that the use of the counterweight ill to bias thearmature to its one extreme position tends to cause the armature to remain in such one extreme position longer than it remains-in its opposite extreme position during operation of the relay, thus causing an undersirable difference in the on time of the two lamps of the signal or signals which are controlled by the relay,'and in order to eliminate this difference I provide means independent of the washers l for adjusting the time characteristics of the magnet toward which the armature 8 is biased by the counterweight, whereby the two on times can be equalized. As here shown, this means comprises an L-shaped magnetic shunt 11, one leg I'l' of which extends between the pole pieces 2 and 3 at their confronting sides, and the other leg ll of which is adjustably secured to the pole pieceli by means of screws I8 which pass through-elongated holes I! in the leg I :l and are screwed into tapped holes formed in the pole piece 3*. This shunt bypasses away from the armature a portion of the flux set up in the U-shaped magnet formed by the cores 2 and 3, the backstrap 4 and the winding 6, and thereby decreases the torque exerted on the armature by this magnet. This shunt also changes the reluctance of the magnetic circuit of the associated magnet, thus changing the time constants of the magnet. The portion of the flux which is bypassed from the armature will depend, of course, upon the adjustment 'of the'shunt, and it will be seen, therefore, that by adjusting the shunt ll the inductive characteristics of the magnet toward which the counterweight biases thearmature can be changed sufliciently to cause each ofthe warning lamps to be alternately energizedforequal lengths of time.

'It should be particularly pointed out that while the shun I1 is provided primarily for the purpose of equalizing any differences which may exist in the time the armature remains in its two extreme positions caused by the provision of the counterweight Ill, this shunt also provides a means for equalizingany differences in the times the armature remains in its two extreme positions due to unbalances in the two magnetic circuits resulting from differences in air gaps, difierences in the resistances of or number of turns in, the windings and 6, differences in characteristics of the iron, etc., as Well as any differences which may be caused by unequal pressures exerted. by the contacts on Opposite sides of the pivotal axis of the armature. 'It should :also be pointed out that this shunt may be used on relays which are not provided with a counterweight although the differences in the on times of the lamps which existwhen no counterweight is provided are not usually great enough to necessitate the use of the shunt.

Although I have herein shown .and described only one form of relay embodying my invention, it is understood 'that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In an electromagnetic relay, in combination, an armature pivotally 'mounted intermediate its ends formovement-between two extreme positions and biased to one extreme position, two electromagnets disposed on opposite sides of the pivotal axis of said armature and having poles adjacent said armature for moving said armature between its two extreme positions, and a magnetic path of low reluctance across the poles of one of said electromagnets for adjusting the time characteristics of said one electromagnet to equalize the response of said armature to each magnet.

2. In an electromagnetic relay, in combination,

an armature pivotally mounted intermediate its ends for movementbetween two extreme positions. a counterweight for biasing said armature to one extreme position, two electromagnets disposed on opposite sides of the pivotal axis of said armature, one for'moving said armature to its one extreme position and the other formoving said armature to its other extreme position, means for alternately energizing said magnets to cause said armature to oscillate, and an adjustable means for shunting a portion of the flux set up by said one electromagnet away from said armature to compensate for any diiferences caused by said counterweight in the lengths of time during which the armature remains in its two extreme positions.

3. Inianelectromagnetic relay, in combination,

an armature pivotally mounted intermediate its ends for movement between two extreme positions, means for biasing said armature to one extreme position, two electromagnets one for moving said armature to its one extreme position and the other for moving said armature to its other extreme position, means for supplying the windings of said two electromagnets connected in series with current, means controlled by said armature for short circuiting said one winding or said other winding according as said armature is moved to its one or its other extreme position to cause said armature to oscillate, and an adjustable magnetic shunt for shunting a portion of the flux set up by said one electromagnet away from said armature to compensate for any differences caused by said biasing means in the time intervals during which said armature remains in its two extreme positions.

4. In an electromagnetic relay, in combination, an armature pivotally mounted intermediate its ends for movement between two extreme positions, means for biasing said armature to one extreme position, two electromagnets disposed on opposite sides of the pivotal axis of said armature for moving said armature between its two extreme positions, said two electromagnets being provided with a common magnetic path, means controlled by said armature for energizing the windings of said electromagnets in a manner to cause said armature to oscillate, short circuited windings disposed on said common path for controlling the rate of oscillation of said armature, and adjustable means for shunting a portion of the flux set up by said one electromagnet away from said armature to equalize the time intervals during which said armature remains in its two extreme positions.

5. In an electromagnetic relay, a movable armature, two U-shaped electromagnets for actuating said armature to oppositely disposed positions, each of said electromagnets having a common leg, means for biasing said armature to one position, means for alternately energizing the windings of said electromagnets, means associated with said common leg for adjusting the time lag of the response of said armature to said alternate energizations, and means associated with one of said electromagnets only to adjust the time lag of the response of said armature to the energization of said one electromagnet to equalize any difference in time lag which might exist between successive movements of said armature due to "said biasing means.

6. A relay comprising a first, a second and a third core connected together at one end by a backstrap and provided at the other end with first, second and third pole pieces, respectively, a first winding on said first core and a second winding on said second core, means for alternately energizing said windings in such manner that the fluxes set up in said third core by said two windings traverses said third core in opposite directions, an armature mounted to move toward said first or said second pole piece according as said first or said second winding is energized, short circuited windings on said third core for controlling the rate of growth and decay of the flux set up in said third core by the energization of said windings, means for biasing said armature toward said first pole piece, and a magnetic shunt secured to said first pole piece and movable toward and away from said third pole piece, said shunt being so adjusted that it will compensate for any differences caused by said biasing means in the time intervals which elapse between successive armature movements.

'7. A relay comprising a first, a second and a third core connected together at one end by a backstrap and provided at the other end with first, second and third pole pieces, respectively, a first winding on said first core and a second winding on said second core, an armature mounted to move toward said first or said second pole piece according as said first or said second winding is energized, means for energizing said two windings connected in series, means controlled by said armature for short circuiting the winding on the core toward which the armature is moved by the energization of such winding to cause said armature to oscillate, short circuited windings on said third core for controlling the rate of growth and decay of the flux set up in said third core by the energization of said windings, means for biasing said armature toward said first pole piece, and a magnetic shunt secured to said first pole piece and movable toward and away from said third pole piece, said shunt being so adjusted that it will compensate for any differences caused by said biasing means in the time intervals during which said armature remains in its two extreme positions.

BENJAMIN MISHELEVICH. 

